1. Field of the Invention
The present invention relates to an electrophoresis display, and more particularly to an electrophoresis display that is adaptive for decreasing a drive voltage, and a driving method thereof.
2. Description of the Related Art
If a material having electric charge is placed in DC electric field, the material peculiarly moves in accordance with electric charges, the size and shape of molecules and the like. Such a movement is named ‘Electrophoresis’. Recently, a display using electrophoresis has been developed and attention has been paid thereto as a medium with which a conventional paper medium could be replaced.
The display using electrophoresis has been disclosed in U.S. Pat. Nos. 7,012,600 and 7,119,772. The electrophoresis display of the related art compares current state images with next state images for each cell by use of a look-up table (LUT) 1, a plurality of memories 2 to 4 and a frame counter 5, as shown in FIG. 1, thereby determining the data V1 to Vn which are to be supplied to each cell for a plurality of frame periods, as a result.
The data V1 to Vn outputted from the look-up table 1 are digital data such as ‘00’, ‘01’, ‘10’ and ‘11’, and are changed to voltages of three states which are applied to a pixel electrode of each cell, that is, Ve+, Ve−, and Ve0. ‘00’ and ‘11’ in the digital data is changed to 0V, ‘01’ is changed to Ve+(+15V), and ‘10’ is changed to Ve−(−15V).
FIG. 2 shows an example of a drive waveform which is supplied for a plurality of frame periods in accordance with a data written in the current state and a data to be written in the next state. In FIG. 2, ‘W(11)’ represents a white gray level, ‘LG(10)’ represents a bright gray level, ‘DG(01)’ represents a dark gray level, and ‘B(00)’ represents a black gray level. And, the number written under the drive waveform is the number of frames.
A DC common voltage Vcom is supplied to a common electrode which is opposite to a pixel electrode. A positive data voltage Ve+ supplied to the pixel electrode is a voltage which is higher than the DC common voltage Vcom, and a negative data voltage Ve− is a voltage which is lower than the DC common voltage Vcom.
A method of driving the electrophoresis display has problems: firstly, the storage capacity of a memory 4 becomes that much larger because the digital data of each cell is 2 bits; secondly, since a reset voltage waveform, a stable voltage waveform, and an entry data voltage waveform are sequentially supplied to a pixel electrode for the plurality of frame periods so as to allow all cells to be uniformed to a bistable state after initializing the previous cell state. Thus, time which is required at a data update, is increased. On the other hand, a data voltage can be boosted so as to decrease time which is spent at the data update. However, elements within a data drive integrated circuit (D-IC) should be configured as high voltage elements because of a high data voltage, thus the size of the D-IC should be that much larger and the cost thereof is increased.